JP2020522144A - Heat sink and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a heat sink (100), the heat sink comprising a substantially planar, solid slab (101) provided with a plurality of fluid flow paths, the plurality of fluid flow paths comprising an inlet (110) to the slab. To the outlet (120), the plurality of channels being at least two main channels (10, 10) interconnected by at least a plurality of bridging channels (31-34, 36-37). 20), the plurality of bridging channels are not further branched between their respective attachment points to their main channels, and the bridging channels (31-34, 36-37) are in the flow direction. Has a locally increasing cross section, and the bridging channels (31-34, 36-37) have a locally decreasing cross section in the flow direction downstream of the local increase in the cross section. The present invention also relates to a method for manufacturing a heat sink.

Description

FIELD OF THE INVENTION The present invention relates to the field of heat sinks.

BACKGROUND A heat sink is a physical structure that transfers the heat generated by another device to a fluidized medium, which is then guided away from the device.

Component cooling is a recurring problem in the industry. One reason is that the lifetime of components is very often highly dependent on operating temperature. Therefore, active cooling is applied to the components to keep the maximum temperature below a certain limiting temperature. Examples of such components range from lasers to engines to power electronics. Also, the product may require cooling during manufacture. This is the case, for example, in the case of casting. By applying active cooling during casting, cycle time is reduced resulting in increased productivity. However, inadequate cooling can result in poor product quality.

The liquid cooling plate is basically a heat sink through which the liquid cooling liquid flows. Various heat sources are mounted on the cooling plate. A common design for such common cooling plates is a metal plate with one meandering cooling channel extending across all heat sources. However, in the conventional meandering heat sink, the fluid becomes hot along the meandering flow path, which adversely affects the cooling near the ends of the flow path.

T. Van Oevelen (KU Leuven, November 2014) dissertation “Optimal Heat Sink Design for Liquid Cooling of Electronics”, advanced numerical design for micro heat sink The method is detailed. Two approaches are described: shape optimization of a single microchannel and heatsink topology optimization. The problem of topology optimization is solved by optimally controlling the fictitious porosity used in the two-dimensional model used to distinguish solids from fluids. According to this paper, improvements are theoretically made to the serpentine heat sink, but in terms of, for example, reducing the temperature gradient, a model in which the "solid" part of the plate is porous and basically infinitely wide. Because of the possibility of using narrow channels of the result, the result is not practical in actual manufacturing.

German Patent Application Publication No. 10 2011 118483 in the name of Volkswagen DE discloses a heat exchanger including a casing whose longitudinal direction is oriented from the front side to the rear side. The configured heat transfer surface of the solid portion has a planar base surface having heat transfer elements spaced apart from each other. The heat transfer elements are arranged as protrusions parallel to the base. The oriented cross-section of the base is set with different widths perpendicular to the longitudinal direction and different lengths parallel to the longitudinal direction such that the maximum length is greater than the maximum width.

U.S. Patent Application Publication No. 2014/091453 assigned to Toyota Industries Corporation discloses a cooling device including a base and a plurality of heat radiation fins. The substrate includes an outer surface, an inner surface, an inlet, and an outlet. A heating element is connected to the outer surface of the base. The radiating fin is provided inside the base body near the heating element. The radiating fins are arranged from the inlet to the outlet. Each radiating fin has a cross section having a dimension in the flow direction of the cooling medium and a dimension in the width direction orthogonal to the flow direction of the cooling medium. The dimension in the flow direction is larger than the dimension in the lateral direction. The radiating fins are arranged laterally at a predetermined distance.

US Patent Application Publication No. 2009/145581 in the name of Paul Hoffman et al. discloses a non-linear fin heat sink for uniform heat dissipation/removal from a device, which provides a small and relatively lightweight heat sink. Although provided, the heat generation is non-uniform across the device. The heat sink has overhanging surface protrusions, which are optimal for the local physical properties of the coolant medium, because the heat sink cancels out the temperature rise of the coolant medium and enhances the cooling with respect to the temperature of the coolant medium. Convective heat transfer and conductive heat transfer and flow that allow to provide cooling efficiency and to be used with fluids to achieve heat transfer, such as cooling liquids, gas cooling liquids, or combinations thereof. It is claimed that it is molded optimally, recognizing resistance. In addition, the heat sink features turbulence enhancement of the cooling liquid flow by the fin array through which the cooling liquid flow passes, such fin array providing optimal cooling while simultaneously reducing volume and flow resistance. It features nonlinear shapes, spacing, and height patterns.

A. Kosar et al. "TCPT-2006-096.R2: Micro Scale pin fin Heat Sinks-Parametric Performance Evaluation Study" IEEE Transactions on Components and Packaging Technologies, vol. 30 , no. 4 presents an experimental parametric study of heat transfer and pressure drop associated with forced flow of deionized water for five micro-pin fin heat sinks of different spacing, configuration and shape. There is. Nusselt numbers and coefficients of friction were obtained for Reynolds numbers in the range 14-720. Thermal and hydraulic results were obtained to evaluate and compare the performance of heat sinks with a fixed mass flow rate, a fixed pressure drop, and a fixed pumping capacity. Two distinct regions of the dependence of the Nusselt number on the Reynolds number, separated by the critical Reynolds number for the non-streamline Pinfin device, were identified, while the streamliner did not show a change in slope. The effect of pin spacing, shape, and placement on the coefficient of friction and heat transfer was consistent with existing literature. These results show that the use of streamlined pin fin heatsinks significantly increases the thermal and hydraulic performance of the heatsinks, but only moderate Reynolds numbers.

These existing solutions do not seem to offer a good trade-off between thermal efficiency and pressure drop. Therefore, there remains a need for improved heat sinks.

Overview Embodiments of the present invention present new cooling solutions enabled by topology optimization, especially for use in industrial environments.

According to one embodiment of the present invention, a heat sink is provided, the heat sink comprising a substantially planar, solid slab, a plurality of fluid passages being provided, the plurality of fluid passages being at an inlet of the slab. A plurality of flow passages, the plurality of flow passages including at least two main flow passages interconnected by at least a plurality of bridging flow passages, the plurality of bridging flow passages including the main flow passages. No further divergence between their respective attachment points to the bridging channel has a locally increasing cross section in the flow direction, the bridging channel being downstream of said local increase in cross section. And has a cross section that locally decreases in the flow direction.

The term “slab” is used to describe a plate-like structure having substantially parallel top and bottom surfaces and a perimeter, the top and/or bottom surfaces being in contact with a heat source from which heat is removed. The perimeter typically defines a rectangle, although other polygonal and non-polygonal shapes may be preferred depending on the application.

The term "main channel" is used herein to describe the extent of channels interconnected by other channels. The heat sink according to the present invention may have more than one main flow path, which main flow paths typically exhibit some symmetrical configuration, but are not required.

Some or all of the flow passages interconnecting the pairs of main flow passages can be considered as "brishing flow passages" in the sense of the claimed invention, increasing locally in the flow direction, Downstream of the positive increase, the bridging channel is provided with a cross-section that decreases locally in the flow direction, and the bridging channel does not further branch between its respective attachment points to the main channel. Represents.

It is surprising to the inventors that the present invention provides a more optimal balance between pressure drop and flow rate, in particular by providing a bridging channel with a locally increasing cross section in the flow direction. It is based on the knowledge that should be. Acceptable pressure drop is typically determined by external conditions (eg, the characteristics of the coolant pump used), thus maximizing fluid flow (and hence heat transfer) for a given given pressure This is a property that heat sinks are highly demanded. In the literature, theoretical consideration suggests the use of a channel that narrows in the direction of flow, but contrary to this suggestion, by using a bridging channel that exhibits locally expanding stages, a surprisingly good flow rate is achieved. Was obtained.

Furthermore, the bridging channel narrows again downstream of the constriction described above, before reaching the main channel carrying the fluid. The inventors have discovered that such an arrangement allows for a wider "middle section" of bridging channels that suppresses pressure drop across the channels. In particular, the combination of the wider "middle section" and the constrictions at the inflow and outflow of the bridging channel allows an optimal design trade-off between pressure loss across the channel and waste heat efficiency.

In one embodiment of the heat sink according to the present invention, the main flow path has a minimum cross section that is larger than the maximum cross section of the bridging flow path.

In some embodiments of the heat sink according to the present invention, the main flow path has at least 1/3, preferably at least 1/2, more preferably at least 2/3, or most preferably the outer dimension of the heat sink in the flow direction. It follows a substantially linear trajectory for up to 3/4.

The main flow path can be composed of a plurality of substantially straight sections of substantially the same length, eg, a length that meets the minimum lengths described above.

With these arrangements, the main flow path defines the overall flow of cooling fluid through the slab, and the bridging flow path has a design that locally adjusts the amount of heat that can be absorbed and wasted per unit area. It will be possible.

In one embodiment of the heat sink according to the invention, this local increase in cross section begins at the point of connection with one of the main channels located upstream of the bridging channel.

In this embodiment, the bridging channels present a cross-sectional constriction at the point where they are connected to the main channel through which they flow. The inventors have a particularly effective feature that such constrictions regulate the mass flow rate through such bridging channels, thereby improving heat exchange and waste heat at these points. I was discovered.

In some embodiments of the heat sink according to the present invention, the portion of the solid slab that remains between the fluid flow paths forms islands that do not exhibit multiple axes of symmetry, resulting in different island shapes.

In this embodiment, the islands (also called "fins") exhibit some geometrical change, allowing for changes in heat transfer characteristics along the entire path of the cooling fluid.

In one embodiment of the heat sink according to the present invention, the inlet and/or the outlet are provided around the slab.

It is likewise possible to have the inlet and/or the outlet on the major surface of a substantially planar, solid slab, but the entire heat sink remains substantially planar, thereby making it usable. The more efficient use of space with a limited installation height is an advantage of having inlets and outlets around.

In some embodiments of the heat sink according to the present invention, the plurality of fluid flow paths have a common minimum width.

It is an advantage of this embodiment that multiple channels can be manufactured in the slab in the same production process. For example, a common minimum width of 0.1 mm makes the channels suitable for manufacturing such as by CNC milling, while a common minimum width of 0.5 mm is obtained by metal printing using an SLM.

In one embodiment of the heat sink according to the present invention, the substantially planar and solid slab is provided on one surface of the major surface having the lid, the lid being between the plurality of flow paths. Is secured by connecting means which engage the slab material present in the.

It is an advantage of this embodiment that known production processes such as CNC milling allow the production of slabs with multiple channels, whereby the channels are closed by a lid at the open end. They do not interfere with the cooling efficiency because the connecting means (which may include conventional connectors such as screws or bolts, but also adhesives and welds) engage the slab material present between the channels.

According to one aspect of the invention, there is provided a method of manufacturing a heat sink as described above, the method comprising cutting a quantity of raw material into substantially planar, solid slab sizes and a plurality of streams. Substantially planar, such that the passage comprises at least two main passages interconnected by at least a plurality of bridging passages and the bridging passages have a locally increasing cross section in the flow direction. Machining a plurality of channels into a substantially planar solid slab to a depth less than the total thickness of the solid slab with a substantially planar lid on the machined slab. And arranging in.

The technical effects and advantages of the embodiments of the method according to the invention correspond, mutatis mutandis, to the technical effects and advantages of the corresponding embodiments of the heat sink according to the invention.

These and other features of embodiments of the present invention are described in more detail below with reference to the accompanying drawings.

It is a figure which shows the two-dimensional image of 1st Embodiment of the heat sink which concerns on this invention. It is a figure which shows the two-dimensional image of 2nd Embodiment of the heat sink which concerns on this invention. It is a figure which shows the two-dimensional image of 3rd Embodiment of the heat sink which concerns on this invention. FIG. 6 illustrates an exemplary heat sink having a tortuous flow path as known in the art. FIG. 6 shows a flow chart of an embodiment of the method according to the invention.

Description of Embodiments As mentioned above, a heat sink is a physical structure that transfers heat generated by other devices to a liquid medium (hereinafter also referred to as a "cooling liquid"), which liquid medium is then transferred to the device. You will be guided away from. The liquid cooling plate is basically a heat sink through which the liquid cooling liquid flows. Heat transfer is affected by the flow characteristics of the cooling liquid passing through the channels of the liquid cooling plate (for example, whether the flow is laminar or turbulent), which depends on the shape of the channels, the cooling liquid. Depends on the nature and flow rate of. Efficient heat transfer is obtained by convection in the cooling liquid.

The inventors have discovered that a particular brand new design of the cooling plate liquid flow path is preferred to meet certain criteria such as reduced thermal expansion, lower maximum temperature, more uniform surface temperature. The design according to the present invention is adaptable to meet applicable constraints such as assembly constraints (screws), manufacturing constraints, structural integrity, and limited pressure drop.

Generally, the change in the flow path cross section required in the present invention can be obtained by changing the width and/or the depth of the flow path. Since this description refers to a two-dimensional drawing, it is assumed that all changes in cross section are obtained by changes in width only, but this is done for clarity only and is not general. ..

FIG. 1 is a diagram showing a two-dimensional image of a first embodiment of a heat sink according to the present invention.
The heat sink 100 comprises a substantially planar, solid slab provided with a plurality of fluid flow paths. A plurality of fluid flow passages are formed to carry the cooling liquid from the slab inlet 110 to the outlet 120. In the present embodiment, the slab is bounded by impermeable edges around which the inlet 110 and the outlet 120 are interruptions, respectively, through which the coolant enters the heat sink 100. Alternatively, it is separated from the heat sink 100. Since the inlet 110 and outlet 120 are located on both sides of the slab 101, the cooling liquid basically travels through the slab from left to right.

The plurality of channels include at least two main channels 10, 20 interconnected by at least a plurality of bridging channels 31-34 and 35-37. Those skilled in the art will appreciate that the arrangement of FIG. 1 is symmetrical about the central horizontal axis and, for the sake of simplicity of the drawing and description, the main flow path 20 and bridging flow paths 31-31 in the lower half of FIG. The equivalents of 37 are not numbered, but, of course, their operation will prove to be identical.

The bridging channels 31-34 and 36-37 have cross-sections that locally increase in the flow direction (that is, the direction from the main channel 10 toward the main channel 20 in the figure). In practice, the local increase in cross section begins at the point of connection with the main channel 10 upstream of the bridging channels 31-34 and 36-37 and forms a constriction at or near that point. I understand.

It can also be seen that the bridging channels 31-34 and 36-37 do not branch and that these bridging channels have a cross-section that locally decreases in the flow direction downstream of the local increase in cross-section. .. This is clearly indicated as the second narrowed portion in the vicinity of the connection point with the main flow path 20 located downstream of the bridging flow paths 31 to 34 and 36 to 37.

FIG. 2 is a diagram showing a two-dimensional image of the second embodiment of the heat sink according to the present invention.
The heat sink 100 comprises a substantially planar, solid slab 101 provided with a plurality of fluid channels. A plurality of fluid channels are formed to carry the cooling liquid from the inlet 110 of the slab to the outlet 120. In this embodiment, the slab is bounded by impermeable edges and the inlet 110 and outlet 120 are provided around the slab 101, providing mounting points for fluid transport pipes and the like. Has been. Since the inlet 110 and outlet 120 are located on both sides of the slab 101, the cooling liquid basically travels through the slab from left to right.

The plurality of channels include at least two main channels 10, 20, 20' interconnected by at least a plurality of bridging channels 31, 31'. Those skilled in the art will appreciate that the arrangement of FIG. 1 is symmetrical about the central horizontal axis.

The bridging channels 31, 31' have a cross-section that increases locally in the flow direction (ie, the direction from the main channel 10 towards the main channel 20/20' in the figure). In practice, it can be seen that the local increase in cross section begins at the point of connection with the main channel 10 located upstream of the bridging channels 31, 31' and forms a constriction at or near that point. ..

The channels and the islands of slab material between the channels exhibit an irregular, high entropy pattern, ie symmetry due to the arrangement of inlets and outlets (in the case shown, symmetry about the central horizontal axis). The absence of any other discernible regularity in the pattern is a feature of the embodiments shown in FIGS. Individual islands do not exhibit multiple axes of symmetry, and many different island shapes tend to occur. Some islands have a wedge-shaped feature that matches the approaching flow and divide the flow path into multiple flow paths.

FIG. 3 is a diagram showing a two-dimensional image of the third embodiment of the heat sink according to the present invention.
The heat sink 100 comprises a substantially planar solid slab 101 provided with a plurality of fluid channels. A plurality of fluid channels are formed to carry the cooling liquid from the inlet 110 of the slab to the outlet 120. In this embodiment, the slab is bounded by impermeable edges, and an inlet 110 and an outlet 120 are provided around the slab 101, the slab being for fluid transport pipes and the like. There is a mounting point. Because the inlet 110 and outlet 120 are located on the same side of the slab 101, the cooling fluid basically makes a U-turn through the slab.

The plurality of channels includes at least two main channels 10, 20 interconnected by at least a plurality of bridging channels 31-33.

The bridging channels 31 to 33 have a cross section that locally increases along the flow direction (that is, the direction from the main channel 10 toward the main channel 20 in the drawing). In fact, it can be seen that the local increase in cross section begins at the connection point with the main flow path 10 located upstream of the bridging flow paths 31-33 and forms a constriction at or near that connection point.

It can also be seen that the bridging channels 31-33 do not branch and have a cross section that locally decreases in the flow direction downstream of the local increase in cross section. This is clearly indicated as the second narrowed portion in the vicinity of the connection point with the main flow passage 20 located downstream of the bridging flow passages 31 to 33.

It should be noted that the "main flow path" and the "bridging flow path" do not necessarily have a single unique partition of the flow path, and the requirement that at least two main flow paths are interconnected by at least a plurality of bridging flow paths. In each satisfying embodiment, there is at least one such partition (eg, the partition shown in the respective figures), and the bridging channel has a locally increasing cross section in the flow direction.

Although only one inlet and one outlet are shown throughout the drawings, it is likewise possible to have more than one inlet and/or more than one outlet. Throughout the drawings, the illustrated inlets and outlets are arranged along the perimeter in the plane of the slab, but it is equally possible to have one or more inlets and/or one or more outlets connecting to the main surface of the heat sink. Is possible.

For comparison, FIG. 4 shows an exemplary heat sink having a tortuous flow path as is known in the art. The configuration relates to a water-cooled aluminum heat sink (grey) mounted on a steel plate (black) having a thickness of 0.002 m. This steel plate is a 10 cm×10 cm square. Inlet 110 and outlet 120 are provided at one peripheral edge of the heat sink, both of which have a 1 cm x 1 cm square cross section. One serpentine coolant flow path extends from the inlet 110 to the outlet 120, ie the coolant flow path is the same amount of material as the heat sink according to the invention shown in FIG. 4, ie 60.3% material. Is designed to be.

For the purposes of this comparative simulation, a uniform water velocity of 0.1 m/s is imposed on the inlet side 110. The temperature (T _in ) of the cooling liquid at the inlet is 293K. The steel sheet is uniformly heated from below with a heat flux of 10 kW/m ² .

The thermal performance of the designs of Figures 4 and 5 is measured at the bottom of the steel sheet, which is also the location of the heat source. A comparison of the designs of FIGS. 4 and 5 is as follows.

If the amount of material of the heat sink is the same, the temperature and velocity of the coolant at the inlet are the same, and the positioning is the same at the inlet and the outlet, the average temperature and the maximum temperature are significantly lower in the heat sink according to the invention. I understand.

The same conclusions apply for the inlet temperature T _in , the outlet temperature T, and the thermal resistance R _th defined at the total heat input Q (Q = qA = 10 kW/m ² × 0.01 m ² = 100 W) as shown below. become.

R _th = (T ‐ T _in )/Q
The pressure drop observed on the heat sink according to the present invention is almost an order of magnitude lower than the pressure drop observed on the heat sink according to the prior art, this difference being smaller (cheaper) for better cooling. It has important techno-economic benefits because it represents that a coolant pump can be used.

Flow paths in heat sinks according to the present invention, especially in substantially planar slabs, include milling, laser cutting, etching, 3D printing, sheet metal forming (eg, die forming and hydroforming), and other known manufacturing methods. Can be manufactured in. It is particularly advantageous to design the heat sink 100 according to the present invention so that the plurality of fluid flow paths have a common minimum width suitable for the manufacturing technology.

A specific method of manufacturing the heat sink 100 according to the present invention is shown in FIG. The method includes cutting 1010 a quantity of raw material into a substantially planar, solid slab 101 size to obtain a desired shape. Many heat sinks are rectangular, but other shapes are possible. The plurality of flow channels include at least two main flow channels 10 and 20 interconnected by at least a plurality of bridging flow channels 31 to 37, and the bridging flow channels are locally arranged in the flow direction. 1020 machined into the substantially planar solid slab to a thickness that is less than the total thickness of the substantially planar solid slab to have a substantially increasing cross-section. Finally, a substantially planar lid 102 is placed 1030 on the machined slab 101.

Although the invention has been described with reference to particular embodiments, this is for the purpose of clarity rather than limitation of the invention, the scope of which is referred to the appended claims. Should be decided. It should also be noted that the concepts described herein are applicable to heat exchangers with similar effects.

Claims (9)

A heat sink (100) comprising a substantially planar, solid slab (101) provided with a plurality of fluid channels, the plurality of fluid channels being from an inlet (110) to an outlet of the slab. Formed to carry cooling liquid to (120),
The plurality of flow paths include at least two main flow paths (10, 20) interconnected by at least a plurality of bridging flow paths (31-34, 36-37), the plurality of bridging flow paths comprising: No further divergence between their respective attachment points to said main flow paths (31-34, 36-37),
The bridging channels (31-34, 36-37) have a cross-section that increases locally in the flow direction,
The heat sink, wherein the bridging channels (31-34, 36-37) have a cross section that locally decreases in the flow direction downstream of the local increase in the cross section. The heat sink (100) of claim 1, wherein the main flow path (10, 20) has a minimum cross section that is greater than a maximum cross section of the bridging flow path (31-37). The main flow paths (10, 20) are at least 1/3, preferably at least 1/2, more preferably at least 2/3, or most preferably the outer dimension length of the heat sink (100) in the flow direction. A heat sink (100) according to any one of the preceding claims, which follows a substantially linear trajectory for up to 3/4. A local increase in the cross-section starts from a point of connection with one of the main channels (10) located upstream of the bridging channels (31-37). The heat sink (100) as described. A heat sink (100) according to any one of the preceding claims, wherein the portion of the solid slab that remains between the fluid flow paths forms islands that do not exhibit multiple axes of symmetry, resulting in different island shapes. A heat sink (100) according to any one of the preceding claims, wherein the inlet (110) and/or the outlet (120) are provided around the slab (101). The heat sink (100) of any one of the preceding claims, wherein the plurality of fluid channels have a common minimum width. The substantially planar and solid slab (101) is provided on one of its major surfaces having a lid (102), the lid between the plurality of channels. Heat sink (100) according to any one of the preceding claims, secured by connecting means for engaging existing slab material. A method of manufacturing a heat sink (100) according to any one of the preceding claims, comprising:
Cutting a quantity of raw material to a substantially planar, solid slab (101) size;
The plurality of flow paths include at least two main flow paths (10, 20) interconnected by at least a plurality of bridging flow paths (31 to 37), and the bridging flow paths are locally arranged in a flow direction. A plurality of channels in the substantially planar solid slab to a depth less than the total thickness of the substantially planar solid slab to have a substantially increasing cross section. What to do
Placing a substantially planar lid (102) on the machined slab (101).